The present invention relates to a combinatorial weighing apparatus, and more particularly to a combinatorial weighing apparatus having a reweighing capability for reweighing discharged articles that have been weighed.
Combinatorial weighing apparatus have a plurality of weighing hoppers supplied with batches of articles to be weighed, a plurality of weight detectors for measuring weights of the batches of articles supplied respectively to the weighing hoppers, and a combinatorial computing unit. The weighing hoppers and the weight detectors jointly form weighing machines. The combinatorial computing unit serves to effect a combinatorial arithmetic operation for finding a combination of batch weights (hereinafter referred to as an "optimum combination") equal or closest to a target weight value within an allowable weight range setting. The combinatorial computing unit also controls those weighing machines, which provide an optimum combination, to discharge the weighed articles onto a packing line. The combinatorial computing unit then supplies new batches of articles into the weighing machines from which the articles have been discharged, and repeats the foregoing cycle of combinatorial weighing for a continued automatic weighing process.
The weight sum, indicative of the optimum weight combination as computed by the combinatorial computing unit, is displayed on a display unit.
There are many instances where weighing machines of the foregoing construction are placed in locations subjected to various externally induced disturbances due to vibrations and winds. Where a vibratory supply unit is employed for supplying articles to be weighed into the weighing machines, the weighing machines are directly subjected to vibrations caused by the vibratory unit. Therefore, the weighing machines produce weight detector outputs or weight values containing measurement errors. This sometimes causes the sum of the weights of actually discharged articles to fall outside an allowable weight range setting, that is, smaller than a target weight or greater than an upper weight limit. When such a condition arises, the weighing apparatus is automatically inactivated, and the user has to manually discharge the articles out of the weighing apparatus and start the apparatus again. If it is not desired to shut down the production line for reconditioning the weighing apparatus, then the weighing apparatus must be continuously operated to allow batches of articles having an improper total weight to be discharged, and the packed articles have to be checked for inaccurately weighed products, which are then rejected. Furthermore, articles tend to get stuck to the weighing hoppers, and the total weight of actually discharged articles is liable to differ from the displayed weight.
It has been a conventional practice to incorporate a checker or checking weighing device in a packaging line for checking the weight of articles discharged from the combinatorial weighing apparatus. However, such a checker has been highly expensive and requires a large space for its installation. There is a demand for incorporation of the checker into the weighing machines so as to render the combinatorial weighing apparatus more reliable in operation and meet the requirement of total controllability.